1. Field of the Invention
This invention relates to blood sample collection and more particularly relates to an additive for a blood collection container which facilitates separation of the sample into its components.
2. Background
Blood samples are routinely taken in evacuated glass tubes. Plastic tubes also have been proposed for blood collection. One end of a double-ended needle is inserted into a patient's vein. The other end of the needle then punctures a septum covering the open end of the collection tube so that the vacuum in the tube draws the blood sample through the needle into the tube. Using this technique a plurality of blood samples can be taken using a single needle puncture of the skin.
Prior to analysis, blood samples are routinely clotted and centrifuged. The clotting process is slow, often taking 30 minutes or more to complete. This length of time is unacceptable for many routine blood analysis operations, and as a result clotting activators are often added. Typical activators are diatomaceous earth and particles of inorganic silicates, or biochemicals such as ellagic acid and thromboplastin. In one line of commercial blood collection tubes, a coating of silicate particles in polyvinylpyrrolidone (PVP) is affixed to the inside wall of the tube. When blood enters the tube, it dissolves the PVP releasing the silicate particles to initiate clotting. These finely divided activator particles may not pellet completely with the clot and may thus remain in the serum layer, a detriment for certain blood analyses, and may foul automatic blood analysis instruments.
There is need in the art of blood collection for a blood clot activator that enhances the rate of blood coagulation but which does not remain within the serum layer on centrifugation, thus avoiding potential interference with clinical tests.